A magneto is an electromechanical device used as part of the ignition system for a motor vehicle. The magneto generates electrical energy based on the rotation of the engine. The electrical energy is then supplied to an ignition component, typically a spark plug, which ignites a fuel and air mixture within a cylinder of the engine.
A magneto consists of two main portions, a generating portion and a distributor portion. The generator portion of the magneto is built around a central generator shaft which is connected to an engine crankshaft in such manner that the generator shaft turns in proportional relationship to the crankshaft. Rotation of the shaft within the generator portion of the magneto causes permanent magnets to move in relation to windings of wire, thereby producing an electric current. After electricity is produced, it may be passed through additional coils of wire ("coils") which increase the voltage of the generated electricity. The coils are connected to the distributor portion of the magneto, allowing high voltage electricity to pass to the distributor portion.
The distributor portion is also built around a central shaft which turns in proportional relation to the crankshaft of the engine. A rotating distributor lead within the distributor portion of the magneto is supplied with high voltage electricity from the coils. As the distributor lead rotates within the distributor portion, the lead encounters electrical contacts placed along the circumference of the circle defined by the rotation of the distributor lead. As the distributor lead encounters each electrical contact, the lead imparts high voltage electricity to each respective electrical contact. Each electrical contact is typically connected to an ignition source, such as a spark plug, within the cylinder of a motor engine. The voltage supplied to the electrical contact by the passing distributor lead causes an electrical arc within the attached spark plug that ignites the fuel and air mixture within the cylinder of an internal combustion engine. The electrical contacts are arranged around the circumference of the distributor portion so that the contact of the distributor lead with a particular electrical contact corresponds to the proper time for ignition of the spark plug to which that particular electrical contact is connected. For instance, a magneto engineered for an eight cylinder automotive engine with the eight cylinders firing at regular intervals would have eight electrical contacts evenly spaced at 45 degree intervals around the circumference of the distributor portion. Thus, one complete turn of the distributor portion of the magneto would fire all eight cylinders of the motor engine. As used herein "automotive" refers to a vehicle having four or more wheels.
Magnetos are often used with racing or other high performance automotive engines. High performance engines, producing very high output, utilize fuel and air mixtures which are very "rich", having a much larger ratio of fuel to air than conventional automotive engines. In order to effectively and reliably ignite the mixture rich with gasoline, nitromethane, or other fuel, the ignition system must supply a tremendous amount of energy to the fuel and air mixture.
Typical battery-based ignition systems do not meet the needs of high performance engines. Battery-based ignition systems do not provide the high power electrical energy required for high performance engines, and such systems also require that large and heavy batteries be carried by the vehicle.
Magneto-based ignition systems provide many advantages over traditional battery-based ignition systems. All of these advantages are seemingly equally applicable to motorcycles engines, a motorcycle engine being fundamentally the same as an automobile engine, though smaller and with fewer cylinders. Motorcycle racers and enthusiasts have many of the same concerns as their automobile racing colleagues.
Use of a magneto-based ignition system with a motorcycle engine would provide many benefits to the performance of a motorcycle. As mentioned above, a magneto is capable of producing tremendous electrical energy to ignite very rich fuel/air mixtures which are not properly ignited by battery-based ignition systems. Also, the magneto-based ignition system is considered to be more reliable than a battery-based ignition system because of a lower likelihood of faulty or shorted wiring. Also, performance of a motorcycle with a magneto-based ignition system is improved because the motorcycle does not have to carry a large and heavy battery for the battery-based ignition system.
Use of a magneto-based ignition system for a high performance motorcycle engine greatly increases the safety of the motorcycle engine. High performance motorcycle engines operate at extremely high compression, with timing and ignition being extremely important to the operation of the engine. A misfire, a condition in which the fuel/air mixture within the cylinder fails to properly ignite, within such a high performance engine results in damage to the motor engine or even explosion of the engine. For these reasons, use of a magneto-based ignition system, having a more reliable ignition, provides a great improvement in safety to the rider of a high performance motorcycle. However, motorcycle engines, particularly two cylinder motorcycle engines, have timing angles that do not correspond with automotive magnetos.
What is needed is an apparatus that allows the use of a high performance automotive magneto with a two cylinder motorcycle engine.